Refrigeration and heat pump systems use large amounts of energy and have limited range of temperature difference between the heat source/heat sink and the air or vapor being cooled or heated. They have inherent limits of temperature range because of use of phase change to achieve temperature shift. They also suffer from a “dead band” of wasted energy to create a temperature shift large enough to bridge the gap between the refrigerated side and the heated side. Freon 410 systems have a Coefficient of Performance (COP) which is the amount of energy pumped divided by the work energy which must be added. For heating applications the work energy is included in the heat output, so in general the COP for cooling plus 1 equals the COP for heating.
Refrigerant based heat pumps are used primarily for historical reasons, as equipment and methods exist to create a purely gas phase heat pump. Additionally, to use a gas phase heat pump requires removing energy on the cooled side before heat exchange. That has been assumed to be a liability, as it is mistakenly assumed that removing energy requires expenditure of energy. However, this energy is actually readily available to help compress the vapor to required pressure for the hot side of the cycle, producing a net reduction in expended energy.